P0131
DTC P0131: Primary HO2S (Sensor 1) Circuit Low Voltage1. Reset the PCM.
2. Start the engine. Hold the engine speed at 3000 rpm without load (in Park or neutral) until the radiator fan comes on.
3. Check the primary HO2S (Sensor 1) output voltage with the HDS or a scan tool during acceleration using wide open throttle.
Is there 0.5 V or less?
YES - Go to step 4.
NO - Intermittent failure. The system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the PCM.
4. Check the fuel pressure with the HDS or a scan tool.
Is the fuel pressure between 200-310 kPa (2.0-3.2 kgf/sq.cm, 29-46 psi)?
YES - Go to step 5.
NO - Repair the fuel supply system.
5. Turn the ignition switch OFF.
6. Disconnect the primary HO2S (Sensor 1) 4P connector.
7. Turn the ignition switch ON (II).
8. Check the primary HO2S (Sensor 1) output voltage with the HDS or a scan tool.
Is there 0.5 V or less?
YES - Go to step 9.
NO - Replace the primary HO2S (Sensor 1).
9. Turn the ignition switch OFF.
10. Disconnect PCM connector A (31P).
11. Check for continuity between primary HO2S (Sensor 1) 4P connector terminal No.1 and body ground.
Is there continuity?
YES - Repair short in the wire between the PCM (A6) and the primary HO2S (Sensor 1).
NO - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.